Light-emitting devices such as light-emitting diodes (LEDs) or laser diodes (LDs) using group III-V or II-VI compound semiconductors may realize various colors of light such as, for example, red, green, and blue light, as well as ultraviolet light, thanks to the development of device materials and thin-film growth technique, and may also realize white light having high luminous efficacy by using a fluorescent material or by combining colors. These light-emitting devices have advantages of low power consumption, a semi-permanent lifespan, fast response speed, good safety, and eco-friendly properties compared to existing light sources such as, for example, fluorescent lamps and incandescent lamps.
Accordingly, the application of light-emitting devices has been expanded to a transmission module of an optical communication apparatus, a light-emitting diode backlight, which may substitute for a cold cathode fluorescent lamp (CCFL) constituting a backlight of a liquid crystal display (LCD) apparatus, a white light-emitting diode lighting apparatus, which may substitute for a fluorescent lamp or an incandescent bulb, a vehicle headlight, and a signal lamp.
When such light-emitting devices are realized in a package form, the introduction of outside air such as moisture from outside into the light-emitting device package may deteriorate the reliability thereof.